Research problem and project objectives: Iron deficiency anemia affects 20 percent of the world's population and an even higher proportion of young children. Iron lack with mild anemia has generally not been considered of great consequence, but there is recent evidence that developmental test performance is impaired in young iron deficient children. The reasons for these developmental test score deficits are unknown. It is postulated that differences in affect, alertness, and coordination underlie the lower test scores, but such behaviors have never been studied objectively. This project will compare the behavior of 38 anemic and 46 matched non-anemic infants to characterize the task-related and social behavior of anemic infants, to delineate their patterns of mental, motor, and emotional dysfunction, to correlate the behavior patterns with development test score deficits and to assess the reversibility of any abnormalities with iron treatment. Methods and significance: The behavior of anemic and non-anemic infants and their caregivers during developmental testing and play (before, after short-and long-term oral iron treatment) will be compared by ratings scales specifically designed to detect disturbances attributed to iron lack and by detailed coding of behavior with a recently introduced computer-compatible event recording system. Specific mental, motor, and social impairments in iron deficiency will be identified by an item-by-item analysis of infant development tests. The results of the rating scales and behavior code analyses will be statistically related to development test scores. The effect of short- and long-term oral iron therapy on behavior during developmental testing, on test item failure and on social interaction will be statistically assessed. Demonstrating that iron deficiency anemia is associated with developmental and behavioral abnormalities will document the urgency and early detection of treatment of iron deficiency in millions of affected children.